At present, user terminals such as smartphones, tablets, as well as payment terminals integrate various techniques for the wireless reception and transmission of data: GSM, Wi-Fi, Bluetooth, NFC. These techniques require the use of transceivers and antennas. The transceivers often take the form of chips which are positioned on a printed circuit board or PCB. Certain transceiver chips are multi-standard chips. This means that they can work with several data transmission techniques. To be able to function accurately, a transceiver chip is especially connected to an antenna. The antenna is a device used to radiate electromagnetic waves (as a transmitter) or pick them up (as a receiver).
One of the techniques most recently integrated into user terminals is a technique of contactless reading. For example, contactless transceiver technology is often used in smartphone-type user terminals or in payment terminals. Such a technique is, for example, that of near-field communications (NFC). Near-field communications (NFC) is a technology of high-frequency, short-range, wireless communications. This technology enables the exchange of data between two compatible devices at a maximum distance of the order of ten centimeters. This technology consists of an extension of connection according to the standards defining proximity cards using RFID or (frequency identification) that combines the interface of a smart card and a reader within a single peripheral device.
The implementing of this data transmission technique within terminals does create a number of problems, especially problems of integration: the space available to obtain this integration is highly limited. Indeed, terminals already have numerous communications functions and numerous antennas and it is difficult to add such an antenna in a terminal. There are also other constraints present such as competition between wireless communications functions (frequency bands can be very close to each other, for certain of these functions, and the modules for sending and receiving data can receive disturbances coming from other communications modules).
For example, a payment terminal integrates numerous modules for reading payment cards: smart cards, stripe cards and contactless cards. NFC technology is increasingly being used to make payments.
For the reading of contactless payment cards, the payment terminal needs to be equipped with a contactless communications antenna. Given the constraints of integration, compactness and ergonomy, the contactless antenna of the terminal is usually situated in the housing of the printer or around the screen of the payment terminal. Besides, in the context of a payment terminal, the payment transaction needs to be made within a predetermined time span. The contactless antenna must therefore enable clear reading (i.e. reading as undisturbed as possible) and fast reading of data coming from a contactless payment card. This is one of the requirements on which the making of a contactless antenna is based.
Thus, in the case of a contactless communications system the antenna of which is situated around the screen of the payment terminal, when the user wishes to make payment by means of his contactless card or his smartphone, he brings this card or smartphone closer to the screen. The designers of payment terminals have indeed deemed it to be necessary for the antenna used for the contactless payment (contactless antenna) to be positioned before the place where the user presents his payment means or in proximity to it.
Besides, it is important to understand that the mounting of a payment terminal is a complex operation carried out mainly by hand and that the designers of terminals must take account of this aspect when they design a novel terminal. The addition of a contactless antenna, which must necessarily be close to the external surface of the terminal (so that the radiation of the antenna will be efficient), has therefore been done in the simplest way possible both in terms of mounting and in terms of positioning.
To this end, the contactless antenna is made in the form of a flexible printed circuit board that goes around the screen. This method of designing the contactless antenna is advantageous from a certain viewpoint. Indeed, the mounting of this antenna is extremely simple. It is enough to place the antenna around the screen and connect the flexible circuit to a connector (an FPC connector) that has been pre-soldered to the motherboard of the terminal.
This method for designing a contactless antenna however raises an economic problem. Indeed, when a flexible printed circuit is manufactured, it has to be paid for on the basis of the total surface area occupied by the flexible printed circuit. In other words, since the contactless antenna goes around the screen, a substantial part of the surface area of the flexible printed circuit (the center, which is empty) has to be paid for even though it is not used. It can be easily understood that when the size of a screen is for example 12 cm2, the fact of having to pay for 12 cm2 of a flexible printed circuit whereas only a small part of this surface area is actually used for making the terminal poses a major problem in terms of costs of manufacturing the terminal.
Besides, this positioning of the flexible printed circuit around the screen also raises a problem in terms of interference. Indeed, in the field of payment terminals, the touch-screens used have the special feature of incorporating a metal sheath or envelope, the purpose of which is to enable the screen to withstand electrostatic discharges. Now this metal sheath produces major interference in the antenna when it is used.
It has recently been proposed to position the wireless communications antenna on the rim of the housing of the printer paper roll. This approach is promising because it appreciably reduces interference received from the screen especially.
In this case, the antenna is constituted by a coil of copper wire in a trough made for this purpose in an internal plastic element of the payment terminal. The method for mounting the antenna consists in winding the copper wire around the plastic part. This approach too causes a problem because it requires substantial space for the antenna. Indeed, to obtain appropriate performance in the antenna, suitable for payment, it is necessary to make at least two loops with a copper wire. These loops lead to an overlapping or straddling of the copper wires and therefore make it necessary to provide sufficient space for this straddling on the internal plastic part. Now since the constraints of compactness are very great, this approach is especially unsuited to payment terminals.
It is therefore necessary to have available a solution for the manufacture and mounting of an antenna that can resolve these problems of the prior art.